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Erythromycin
Overview
What is Erythromycin?
Erythromycin Base Filmtab (erythromycin tablets, USP) is an
antibacterial product containing erythromycin, USP, in a unique, nonenteric film
coating for oral administration. Erythromycin Base Filmtab tablets are available
in two strengths containing either 250 mg or 500 mg of erythromycin base.
Erythromycin is produced by a strain of (formerly )
and belongs to the macrolide group of antibiotics. It is basic and readily forms
salts with acids. Erythromycin is a white to off-white powder, slightly soluble
in water, and soluble in alcohol, chloroform, and ether. Erythromycin is known
chemically as (3R*, 4S*, 5S*, 6R*, 7R*, 9R*, 11R*, 12R*, 13S*,
14R*)-4-[(2,6-dideoxy-3-C-methyl-3-O-methyl-α-L--hexopyranosyl)oxy]-14-ethyl-7,12,13-trihydroxy-3,5,7,9,11,13-hexamethyl-6-[[3,4,6-trideoxy-3-(dimethylamino)-β-D--hexopyranosyl]oxy]oxacyclotetradecane-2,10-dione. The
molecular formula is CHNO, and the molecular weight is 733.94. The structural formula
is:
Colloidal silicon dioxide, croscarmellose sodium, crospovidone,
D&C Red No. 30 Aluminum Lake, hydroxypropyl cellulose, hypromellose,
hydroxypropyl methylcellulose phthalate, magnesium stearate, microcrystalline
cellulose, povidone, polyethylene glycol, propylene glycol, sodium citrate,
sodium hydroxide, sorbic acid, sorbitan monooleate, talc, and titanium dioxide.
What does Erythromycin look like?
What are the available doses of Erythromycin?
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What should I talk to my health care provider before I take Erythromycin?
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How should I use Erythromycin?
To reduce the development of drug-resistant bacteria and maintain
the effectiveness of Erythromycin Base Filmtab tablets and other antibacterial
drugs, Erythromycin Base Filmtab tablets should be used only to treat or prevent
infections that are proven or strongly suspected to be caused by susceptible
bacteria. When culture and susceptibility information are available, they should
be considered in selecting or modifying antibacterial therapy. In the absence of
such data, local epidemiology and susceptibility patterns may contribute to the
empiric selection of therapy.
Erythromycin Base Filmtab tablets are indicated in the treatment of
infections caused by susceptible strains of the designated microorganisms in the
diseases listed below:
Upper respiratory tract infections of mild to moderate degree caused by ; ; (when used
concomitantly with adequate doses of sulfonamides, since many strains of are not susceptible to the erythromycin
concentrations ordinarily achieved). (See appropriate sulfonamide labeling for
prescribing information.)
Lower respiratory tract infections of mild to moderate severity caused by
or .
Listeriosis caused by .
Respiratory tract infections due to .
Skin and skin structure infections of mild to moderate severity caused by
or (resistant staphylococci may emerge
during treatment).
Pertussis (whooping cough) caused by . Erythromycin is effective in eliminating the organism from the
nasopharynx of infected individuals, rendering them noninfectious. Some clinical
studies suggest that erythromycin may be helpful in the prophylaxis of pertussis
in exposed susceptible individuals.
Diphtheria: Infections due to , as an adjunct to antitoxin, to prevent establishment of carriers and to
eradicate the organism in carriers.
Erythrasma - In the treatment of infections due to .
Intestinal amebiasis caused by (oral erythromycins only). Extraenteric amebiasis requires
treatment with other agents.
Acute pelvic inflammatory disease caused by : Erythrocin Lactobionate-I.V.
(erythromycin lactobionate for injection, USP) followed by erythromycin base
orally, as an alternative drug in treatment of acute pelvic inflammatory disease
caused by in female patients with a
history of sensitivity to penicillin. Patients should have a serologic test for
syphilis before receiving erythromycin as treatment of gonorrhea and a follow-up
serologic test for syphilis after 3 months.
Erythromycins are indicated for treatment of the following infections caused
by : conjunctivitis of the
newborn, pneumonia of infancy, and urogenital infections during pregnancy. When
tetracyclines are contraindicated or not tolerated, erythromycin is indicated
for the treatment of uncomplicated urethral, endocervical, or rectal infections
in adults due to .
When tetracyclines are contraindicated or not tolerated, erythromycin is
indicated for the treatment of nongonococcal urethritis caused by .
Primary syphilis caused by .
Erythromycin (oral forms only) is an alternative choice of treatment for primary
syphilis in patients allergic to the penicillins. In treatment of primary
syphilis, spinal fluid should be examined before treatment and as part of the
follow-up after therapy.
Legionnaires' Disease caused by . Although no controlled clinical efficacy studies have been
conducted, and limited preliminary clinical
data suggest that erythromycin may be effective in treating Legionnaires'
Disease.
Penicillin is considered by the American Heart Association to be
the drug of choice in the prevention of initial attacks of rheumatic fever
(treatment of infections of
the upper respiratory tract e.g., tonsillitis, or pharyngitis). Erythromycin is indicated for the treatment of
penicillin-allergic patients. The therapeutic dose should be administered for
ten days.
Penicillin or sulfonamides are considered by the American Heart
Association to be the drugs of choice in the prevention of recurrent attacks of
rheumatic fever. In patients who are allergic to penicillin and sulfonamides,
oral erythromycin is recommended by the American Heart Association in the
long-term prophylaxis of streptococcal pharyngitis (for the prevention of
recurrent attacks of rheumatic fever).
Optimal blood levels are obtained when Erythromycin Base Filmtab
tablets are given in the fasting state (at least ½ hour and preferably 2 hours
before meals).
The usual dosage of Erythromycin Base Filmtab is one 250 mg
tablet four times daily in equally spaced doses or one 500 mg tablet every 12
hours. Dosage may be increased up to 4 g per day according to the severity of
the infection. However, twice-a-day dosing is not recommended when doses larger
than 1 g daily are administered.
Age, weight, and severity of the infection are important factors
in determining the proper dosage. The usual dosage is 30 to 50 mg/kg/day, in
equally divided doses. For more severe infections this dosage may be doubled but
should not exceed 4 g per day.
In the treatment of streptococcal infections of the upper
respiratory tract (e.g., tonsillitis or pharyngitis), the therapeutic dosage of
erythromycin should be administered for at least ten days.
The American Heart Association suggests a dosage of 250 mg of erythromycin
orally, twice a day in long-term prophylaxis of streptococcal upper respiratory
tract infections for the prevention of recurring attacks of rheumatic fever in
patients allergic to penicillin and sulfonamides.
Oral erythromycin suspension 50 mg/kg/day in 4 divided doses for
at least 2 weeks.
Although the optimal duration of therapy has not been
established, the recommended therapy is oral erythromycin suspension 50
mg/kg/day in 4 divided doses for at least 3 weeks.
Although the optimal dose and duration of therapy have not been
established, the suggested treatment is 500 mg of erythromycin by mouth four
times a day on an empty stomach for at least 7 days. For women who cannot
tolerate this regimen, a decreased dose of one erythromycin 500 mg tablet orally
every 12 hours or 250 mg by mouth four times a day should be used for at least
14 days.
500 mg of erythromycin by mouth four times a day for at least 7
days.
500 mg of erythromycin by mouth four times a day for at least
seven days.
30 to 40 g given in divided doses over a period of 10 to 15
days.
500 mg Erythrocin® Lactobionate-I.V. (erythromycin lactobionate
for injection, USP) every 6 hours for 3 days, followed by 500 mg of erythromycin
base orally every 12 hours for 7 days.
500 mg every 12 hours or 250 mg every 6 hours for 10 to
14 days.
30 to 50 mg/kg/day in divided doses for 10 to 14 days.
Although optimal dosage and duration have not been established,
doses of erythromycin utilized in reported clinical studies were 40 to 50
mg/kg/day, given in divided doses for 5 to 14 days.
Although optimal dosage has not been established, doses utilized
in reported clinical data were 1 to 4 g daily in divided doses.
What interacts with Erythromycin?
Erythromycin is contraindicated in patients with known hypersensitivity to this antibiotic.
Erythromycin is contraindicated in patients taking terfenadine, astemizole, pimozide, or cisapride. (See .)
What are the warnings of Erythromycin?
Cases of tinnitus and reversible or irreversible hearing impairment have been
reported. Usually, reports indicate that furosemide ototoxicity is associated
with rapid injection, severe renal impairment, doses exceeding several times the
usual recommended dose, or concomitant therapy with aminoglycoside antibiotics,
ethacrynic acid, or other ototoxic drugs. If the physician elects to use high
dose parenteral therapy, controlled intravenous infusion is advisable (for
adults, an infusion rate not exceeding 4 mg furosemide per minute has been
used).
There have been reports of hepatic dysfunction, including
increased liver enzymes, and hepatocellular and/or cholestatic hepatitis, with
or without jaundice, occurring in patients receiving oral erythromycin
products.
There have been reports suggesting that erythromycin does not reach the fetus
in adequate concentration to prevent congenital syphilis. Infants born to women
treated during pregnancy with oral erythromycin for early syphilis should be
treated with an appropriate penicillin regimen.
Rhabdomyolysis with or without renal impairment has been reported in
seriously ill patients receiving erythromycin concomitantly with lovastatin.
Therefore, patients receiving concomitant lovastatin and erythromycin should be
carefully monitored for creatine kinase (CK) and serum transaminase levels. (See
package insert for lovastatin.)
Pseudomembranous colitis has been reported with nearly all
antibacterial agents, including erythromycin, and may range in severity from
mild to life threatening. Therefore, it is important to consider this diagnosis
in patients who present with diarrhea subsequent to the administration of
antibacterial agents.
Treatment with antibacterial agents alters the normal flora of the colon and
may permit overgrowth of clostridia. Studies indicate that a toxin produced by
is a primary cause of
"antibiotic-associated colitis".
After the diagnosis of pseudomembranous colitis has been established,
therapeutic measures should be initiated. Mild cases of pseudomembranous colitis
usually respond to discontinuation of the drug alone. In moderate to severe
cases, consideration should be given to management with fluids and electrolytes,
protein supplementation, and treatment with an antibacterial drug clinically
effective against colitis.
What are the precautions of Erythromycin?
Prescribing Erythromycin Base Filmtab tablets in the absence of a
proven or strongly suspected bacterial infection or a prophylactic indication is
unlikely to provide benefit to the patient and increases the risk of the
development of drug-resistant bacteria.
Since erythromycin is principally excreted by the liver, caution should be
exercised when erythromycin is administered to patients with impaired hepatic
function. (See and .)
There have been reports that erythromycin may aggravate the weakness of
patients with myasthenia gravis.
There have been reports of infantile hypertrophic pyloric stenosis (IHPS)
occurring in infants following erythromycin therapy. In one cohort of 157
newborns who were given erythromycin for pertussis prophylaxis, seven neonates
(5%) developed symptoms of non-bilious vomiting or irritability with feeding and
were subsequently diagnosed as having IHPS requiring surgical pyloromyotomy. A
possible dose-response effect was described with an absolute risk of IHPS of
5.1% for infants who took erythromycin for 8-14 days and 10% for infants who
took erythromycin for 15-21 days. Since erythromycin may
be used in the treatment of conditions in infants which are associated with
significant mortality or morbidity (such as pertussis or neonatal infections), the benefit of
erythromycin therapy needs to be weighed against the potential risk of
developing IHPS. Parents should be informed to contact their physician if
vomiting or irritability with feeding occurs.
Prolonged or repeated use of erythromycin may result in an overgrowth of
nonsusceptible bacteria or fungi. If superinfection occurs, erythromycin should
be discontinued and appropriate therapy instituted.
When indicated, incision and drainage or other surgical procedures should be
performed in conjunction with antibiotic therapy.
Patients should be counseled that antibacterial drugs including
Erythromycin Base Filmtab tablets should only be used to treat bacterial
infections. They do not treat viral infections (e.g., the common cold). When
Erythromycin Base Filmtab tablets is prescribed to treat a bacterial infection,
patients should be told that although it is common to feel better early in the
course of therapy, the medication should be taken exactly as directed. Skipping
doses or not completing the full course of therapy may (1) decrease the
effectiveness of the immediate treatment and (2) increase the likelihood that
bacteria will develop resistance and will not be treatable by Erythromycin Base
Filmtab tablets or other antibacterial drugs in the future.
Erythromycin use in patients who are receiving high doses of
theophylline may be associated with an increase in serum theophylline levels and
potential theophylline toxicity. In case of theophylline toxicity and/or
elevated serum theophylline levels, the dose of theophylline should be reduced
while the patient is receiving concomitant erythromycin therapy.
Concomitant administration of erythromycin and digoxin has been reported to
result in elevated digoxin serum levels.
There have been reports of increased anticoagulant effects when erythromycin
and oral anticoagulants were used concomitantly. Increased anticoagulation
effects due to interactions of erythromycin with oral anticoagulants may be more
pronounced in the elderly.
Erythromycin is a substrate and inhibitor of the 3A isoform subfamily of the
cytochrome p450 enzyme system (CYP3A). Coadministration of erythromycin and a
drug primarily metabolized by CYP3A may be associated with elevations in drug
concentrations that could increase or prolong both the therapeutic and adverse
effects of the concomitant drug. Dosage adjustments may be considered, and when
possible, serum concentrations of drugs primarily metabolized by CYP3A should be
monitored closely in patients concurrently receiving erythromycin.
The following are examples of some clinically significant CYP3A based drug
interactions. Interactions with other drugs metabolized by the CYP3A isoform are
also possible. The following CYP3A based drug interactions have been observed
with erythromycin products in post-marketing experience:
Concurrent use of erythromycin and ergotamine or
dihydroergotamine has been associated in some patients with acute ergot toxicity
characterized by severe peripheral vasospasm and dysesthesia.
Erythromycin has been reported to decrease the clearance of
triazolam and midazolam, and thus, may increase the pharmacologic effect of
these benzodiazepines.
Erythromycin has been reported to increase concentrations of
HMG-CoA reductase inhibitors (e.g., lovastatin and simvastatin). Rare reports of
rhabdomyolysis have been reported in patients taking these drugs
concomitantly.
Erythromycin has been reported to increase the systemic exposure
(AUC) of sildenafil. Reduction of sildenafil dosage should be considered. (See
Viagra package insert.)
There have been spontaneous or published reports of CYP3A based
interactions of erythromycin with cyclosporine, carbamazepine, tacrolimus,
alfentanil, disopyramide, rifabutin, quinidine, methylprednisolone, cilostazol,
vinblastine, and bromocriptine.
Concomitant administration of erythromycin with cisapride, pimozide,
astemizole, or terfenadine is contraindicated. (See .)
In addition, there have been reports of interactions of erythromycin with
drugs not thought to be metabolized by CYP3A, including hexobarbital, phenytoin,
and valproate.
Erythromycin has been reported to significantly alter the metabolism of the
nonsedating antihistamines terfenadine and astemizole when taken concomitantly.
Rare cases of serious cardiovascular adverse events, including
electrocardiographic QT/QT interval prolongation,
cardiac arrest, torsades de pointes, and other ventricular arrhythmias, have
been observed. (See .) In addition,
deaths have been reported rarely with concomitant administration of terfenadine
and erythromycin.
There have been post-marketing reports of drug interactions when erythromycin
was co-administered with cisapride, resulting in QT prolongation, cardiac
arrhythmias, ventricular tachycardia, ventricular fibrillation, and torsades de
pointes, most likely due to the inhibition of hepatic metabolism of cisapride by
erythromycin. Fatalities have been reported. (See ).
Erythromycin interferes with the fluorometric determination of
urinary catecholamines.
Long-term (2-year) oral studies conducted in rats with
erythromycin base did not provide evidence of tumorigenicity. Mutagenicity
studies have not been conducted. There was no apparent effect on male or female
fertility in rats fed erythromycin (base) at levels up to 0.25 percent of
diet.
There is no evidence of teratogenicity or any other adverse
effect on reproduction in female rats fed erythromycin base (up to 0.25 percent
of diet) prior to and during mating, during gestation, and through weaning of
two successive litters. There are, however, no adequate and well-controlled
studies in pregnant women. Because animal reproduction studies are not always
predictive of human response, this drug should be used during pregnancy only if
clearly needed.
The effect of erythromycin on labor and delivery is
unknown.
Erythromycin is excreted in human milk. Caution should be
exercised when erythromycin is administered to a nursing woman.
See and .
What are the side effects of Erythromycin?
The most frequent side effects of oral erythromycin preparations
are gastrointestinal and are dose-related. They include nausea, vomiting,
abdominal pain, diarrhea and anorexia. Symptoms of hepatitis, hepatic
dysfunction and/or abnormal liver function test results may occur. (See .)
Onset of pseudomembranous colitis symptoms may occur during or after
antibacterial treatment. (See .)
Erythromycin has been associated with QT prolongation and ventricular
arrhythmias, including ventricular tachycardia and torsades de pointes.
Allergic reactions ranging from urticaria to anaphylaxis have occurred. Skin
reactions ranging from mild eruptions to erythema multiforme, Stevens-Johnson
syndrome, and toxic epidermal necrolysis have been reported rarely.
There have been rare reports of pancreatitis and convulsions.
There have been isolated reports of reversible hearing loss occurring chiefly
in patients with renal insufficiency and in patients receiving high doses of
erythromycin.
What should I look out for while using Erythromycin?
Erythromycin is contraindicated in patients with known
hypersensitivity to this antibiotic.
Erythromycin is contraindicated in patients taking terfenadine, astemizole,
pimozide, or cisapride. (See .)
There have been reports of hepatic dysfunction, including
increased liver enzymes, and hepatocellular and/or cholestatic hepatitis, with
or without jaundice, occurring in patients receiving oral erythromycin
products.
There have been reports suggesting that erythromycin does not reach the fetus
in adequate concentration to prevent congenital syphilis. Infants born to women
treated during pregnancy with oral erythromycin for early syphilis should be
treated with an appropriate penicillin regimen.
Rhabdomyolysis with or without renal impairment has been reported in
seriously ill patients receiving erythromycin concomitantly with lovastatin.
Therefore, patients receiving concomitant lovastatin and erythromycin should be
carefully monitored for creatine kinase (CK) and serum transaminase levels. (See
package insert for lovastatin.)
Pseudomembranous colitis has been reported with nearly all
antibacterial agents, including erythromycin, and may range in severity from
mild to life threatening. Therefore, it is important to consider this diagnosis
in patients who present with diarrhea subsequent to the administration of
antibacterial agents.
Treatment with antibacterial agents alters the normal flora of the colon and
may permit overgrowth of clostridia. Studies indicate that a toxin produced by
is a primary cause of
"antibiotic-associated colitis".
After the diagnosis of pseudomembranous colitis has been established,
therapeutic measures should be initiated. Mild cases of pseudomembranous colitis
usually respond to discontinuation of the drug alone. In moderate to severe
cases, consideration should be given to management with fluids and electrolytes,
protein supplementation, and treatment with an antibacterial drug clinically
effective against colitis.
What might happen if I take too much Erythromycin?
In case of overdosage, erythromycin should be discontinued.
Overdosage should be handled with the prompt elimination of unabsorbed drug and
all other appropriate measures should be instituted.
Erythromycin is not removed by peritoneal dialysis or hemodialysis.
How should I store and handle Erythromycin?
Store at 25°C (77°F); excursions permitted to 15 to 30°C (59 to 86°F) [see USP Controlled Room Temperature].Erythromycin Base Filmtab tablets (erythromycin tablets, USP) are supplied as pink, unscored oval tablets in the following strengths and packages.Store below 86°F (30°C). Keep tightly closed.Erythromycin Base Filmtab tablets (erythromycin tablets, USP) are supplied as pink, unscored oval tablets in the following strengths and packages.Store below 86°F (30°C). Keep tightly closed.
Clinical Information
Chemical Structure
No Image foundClinical Pharmacology
Orally administered erythromycin base and its salts are readily
absorbed in the microbiologically active form. Interindividual variations in the
absorption of erythromycin are, however, observed, and some patients do not
achieve optimal serum levels. Erythromycin is largely bound to plasma proteins.
After absorption, erythromycin diffuses readily into most body fluids. In the
absence of meningeal inflammation, low concentrations are normally achieved in
the spinal fluid but the passage of the drug across the blood-brain barrier
increases in meningitis. Erythromycin crosses the placental barrier, but fetal
plasma levels are low. The drug is excreted in human milk. Erythromycin is not
removed by peritoneal dialysis or hemodialysis.
In the presence of normal hepatic function, erythromycin is concentrated in
the liver and is excreted in the bile; the effect of hepatic dysfunction on
biliary excretion of erythromycin is not known. After oral administration, less
than 5% of the administered dose can be recovered in the active form in the
urine.
Optimal blood levels are obtained when Erythromycin Base Filmtab tablets are
given in the fasting state (at least ½ hour and preferably 2 hours before
meals). Bioavailability data are available from Abbott Laboratories, Dept.
42W.
Erythromycin acts by inhibition of protein synthesis by binding
50 ribosomal subunits of susceptible organisms. It
does not affect nucleic acid synthesis. Antagonism has been demonstrated between erythromycin and clindamycin, lincomycin,
and chloramphenicol.
Many strains of are
resistant to erythromycin alone but are susceptible to erythromycin and
sulfonamides used concomitantly.
Staphylococci resistant to erythromycin may emerge during a course of
erythromycin therapy.
Erythromycin has been shown to be active against most strains of the
following microorganisms, both and in
clinical infections as described in the section.
Corynebacterium diphtheriae
Corynebacterium minutissimum
Listeria monocytogenes
Staphylococcus aureus
Streptococcus pneumoniae
Streptococcus pyogenes
Bordetella pertussis
Legionella pneumophila
Neisseria gonorrhoeae
Chlamydia trachomatis
Entamoeba histolytica
Mycoplasma pneumoniae
Treponema pallidum
Ureaplasma urealyticum
The following data are available, .
Erythromycin exhibits minimal inhibitory
concentrations (MIC's) of 0.5 µg/mL or less against most (≥ 90%) strains of the
following microorganisms; however, the safety and effectiveness of erythromycin
in treating clinical infections due to these microorganisms have not been
established in adequate and well-controlled clinical trials.
Viridans group streptococci
Moraxella catarrhalis
Quantitative methods are used to determine antimicrobial minimum
inhibitory concentrations (MIC's). These MIC's provide estimates of the
susceptibility of bacteria to antimicrobial compounds. The MIC's should be
determined using a standardized procedure. Standardized procedures are based on
a dilution method (broth or agar) or equivalent with
standardized inoculum concentrations and standardized concentrations of
erythromycin powder. The MIC values should be interpreted according to the
following criteria:
A report of "Susceptible" indicates that the pathogen is likely to be
inhibited if the antimicrobial compound in the blood reaches the concentrations
usually achievable. A report of "Intermediate" indicates that the result should
be considered equivocal, and, if the microorganism is not fully susceptible to
alternative, clinically feasible drugs, the test should be repeated. This
category implies possible clinical applicability in body sites where the drug is
physiologically concentrated or in situations where high dosage of drug can be
used. This category also provides a buffer zone which prevents small
uncontrolled technical factors from causing major discrepancies in
interpretation. A report of "Resistant" indicates that the pathogen is not
likely to be inhibited if the antimicrobial compound in the blood reaches the
concentrations usually achievable; other therapy should be selected.
Standardized susceptibility test procedures require the use of laboratory
control microorganisms to control the technical aspects of the laboratory
procedures. Standard erythromycin powder should provide the following MIC
values:
Quantitative methods that require measurement of zone diameters
also provide reproducible estimates of the susceptibility of bacteria to
antimicrobial compounds. One such standardized procedure
requires the use of standardized inoculum concentrations. This procedure uses
paper disks impregnated with 15-µg erythromycin to test the susceptibility of
microorganisms to erythromycin.
Reports from the laboratory providing results of the standard single-disk
susceptibility test with a 15-µg erythromycin disk should be interpreted
according to the following criteria:
Interpretation should be as stated above for results using dilution
techniques. Interpretation involves correlation of the diameter obtained in the
disk test with the MIC for erythromycin.
As with standardized dilution techniques, diffusion methods require the use
of laboratory control microorganisms that are used to control the technical
aspects of the laboratory procedures. For the diffusion technique, the 15-µg
erythromycin disk should provide the following zone diameters in these
laboratory test quality control strains:
Non-Clinical Toxicology
Erythromycin is contraindicated in patients with known hypersensitivity to this antibiotic.Erythromycin is contraindicated in patients taking terfenadine, astemizole, pimozide, or cisapride. (See .)
There have been reports of hepatic dysfunction, including increased liver enzymes, and hepatocellular and/or cholestatic hepatitis, with or without jaundice, occurring in patients receiving oral erythromycin products.
There have been reports suggesting that erythromycin does not reach the fetus in adequate concentration to prevent congenital syphilis. Infants born to women treated during pregnancy with oral erythromycin for early syphilis should be treated with an appropriate penicillin regimen.
Rhabdomyolysis with or without renal impairment has been reported in seriously ill patients receiving erythromycin concomitantly with lovastatin. Therefore, patients receiving concomitant lovastatin and erythromycin should be carefully monitored for creatine kinase (CK) and serum transaminase levels. (See package insert for lovastatin.)
Pseudomembranous colitis has been reported with nearly all antibacterial agents, including erythromycin, and may range in severity from mild to life threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhea subsequent to the administration of antibacterial agents.
Treatment with antibacterial agents alters the normal flora of the colon and may permit overgrowth of clostridia. Studies indicate that a toxin produced by is a primary cause of "antibiotic-associated colitis".
After the diagnosis of pseudomembranous colitis has been established, therapeutic measures should be initiated. Mild cases of pseudomembranous colitis usually respond to discontinuation of the drug alone. In moderate to severe cases, consideration should be given to management with fluids and electrolytes, protein supplementation, and treatment with an antibacterial drug clinically effective against colitis.
Effect of other drugs on LEVITRA
In vivo studies: Cytochrome P450 Inhibitors
Cimetidine (400 mg b.i.d.) had no effect on vardenafil bioavailability (AUC) and maximum concentration (C) of vardenafil when co-administered with 20 mg LEVITRA in healthy volunteers.
Erythromycin (500 mg t.i.d.) produced a 4-fold increase in vardenafil AUC and a 3-fold increase in C when co-administered with LEVITRA 5 mg in healthy volunteers (see ). It is recommended not to exceed a single 5 mg dose of LEVITRA in a 24-hour period when used in combination with erythromycin.
Ketoconazole (200 mg once daily) produced a 10-fold increase in vardenafil AUC and a 4-fold increase in C when co-administered with LEVITRA (5 mg) in healthy volunteers. A 5-mg LEVITRA dose should not be exceeded when used in combination with 200 mg once daily ketoconazole. Since higher doses of ketoconazole (400 mg daily) may result in higher increases in C and AUC, a single 2.5 mg dose of LEVITRA should not be exceeded in a 24-hour period when used in combination with ketoconazole 400 mg daily (see and ).
HIV Protease Inhibitors:
Indinavir (800 mg t.i.d.) co-administered with LEVITRA 10 mg resulted in a 16-fold increase in vardenafil AUC, a 7-fold increase in vardenafil C and a 2-fold increase in vardenafil half-life. It is recommended not to exceed a single 2.5 mg LEVITRA dose in a 24-hour period when used in combination with indinavir (see and ).
Ritonavir (600 mg b.i.d.) co-administered with LEVITRA 5 mg resulted in a 49-fold increase in vardenafil AUC and a 13-fold increase in vardenafil C. The interaction is a consequence of blocking hepatic metabolism of vardenafil by ritonavir, a highly potent CYP3A4 inhibitor, which also inhibits CYP2C9. Ritonavir significantly prolonged the half-life of vardenafil to 26 hours. Consequently, it is recommended not to exceed a single 2.5 mg LEVITRA dose in a 72-hour period when used in combination with ritonavir (see and ).
Other CYP3A4 inhibitors
Other Drug Interactions:
Effects of LEVITRA on other drugs
In vitro studies:
Vardenafil and its metabolites had no effect on CYP1A2, 2A6, and 2E1 (Ki >100 µM). Weak inhibitory effects toward other isoforms (CYP2C8, 2C9, 2C19, 2D6, 3A4) were found, but Ki values were in excess of plasma concentrations achieved following dosing. The most potent inhibitory activity was observed for vardenafil metabolite M1, which had a Ki of 1.4 µM toward CYP3A4, which is about 20 times higher than the M1 C values after an 80 mg LEVITRA dose.
In vivo studies:
Nitrates: The blood pressure lowering effects of sublingual nitrates (0.4 mg) taken 1 and 4 hours after vardenafil and increases in heart rate when taken at 1, 4 and 8 hours were potentiated by a 20 mg dose of LEVITRA in healthy middle-aged subjects. These effects were not observed when LEVITRA 20 mg was taken 24 hours before the NTG. Potentiation of the hypotensive effects of nitrates for patients with ischemic heart disease has not been evaluated, and concomitant use of LEVITRA and nitrates is contraindicated (see ;).
Nifedipine: Vardenafil 20 mg, when co-administered with slow-release nifedipine 30 mg or 60 mg once daily, did not affect the relative bioavailability (AUC) or maximum concentration (C) of nifedipine, a drug that is metabolized via CYP3A4. Nifedipine did not alter the plasma levels of LEVITRA when taken in combination. In these patients whose hypertension was controlled with nifedipine, LEVITRA 20 mg produced mean additional supine systolic/diastolic blood pressure reductions of 6/5 mmHg compared to placebo.
Alpha-blockers:
Blood pressure effects in patients on stable alpha-blocker treatment:
Two clinical pharmacology studies were conducted in patients with benign prostatic hyperplasia (BPH) on stable-dose alpha-blocker treatment for at least four weeks.
Study 1: This study was designed to evaluate the effect of 5 mg vardenafil compared to placebo when administered to BPH patients on chronic alpha-blocker therapy in two separate cohorts: tamsulosin 0.4 mg daily (cohort 1, n=21) and terazosin 5 or 10 mg daily (cohort 2, n=21). The design was a randomized, double blind, cross-over study with four treatments: vardenafil 5 mg or placebo administered simultaneously with the alpha-blocker and vardenafil 5 mg or placebo administered 6 hours after the alpha-blocker. Blood pressure and pulse were evaluated over the 6-hour interval after vardenafil dosing. For BP results see . One patient after simultaneous treatment with 5 mg vardenafil and 10 mg terazosin exhibited symptomatic hypotension with standing blood pressure of 80/60 mmHg occurring one hour after administration and subsequent mild dizziness and moderate lightheadedness lasting for 6 hours. For vardenafil and placebo, five and two patients, respectively, experienced a decrease in standing systolic blood pressure (SBP) of >30 mmHg following simultaneous administration of terazosin. Hypotension was not observed when vardenafil 5 mg and terazosin were administered 6 hours apart. Following simultaneous administration of vardenafil 5 mg and tamsulosin, two patients had a standing SBP of <85 mmHg; two and one patient (vardenafil and placebo, respectively) had a decrease in standing SBP of >30 mmHg. When tamsulosin and vardenafil 5 mg were separated by 6 hours, two patients had a standing SBP <85 mmHg and one patient had a decrease in SBP of >30 mmHg. There were no severe adverse events related to hypotension reported during the study. There were no cases of syncope.
Blood pressure effects (standing SBP) in normotensive men on stable dose tamsulosin 0.4 mg following simultaneous administration of vardenafil 5 mg or placebo, or following administration of vardenafil 5 mg or placebo separated by 6 hours are shown in Figure 3. Blood pressure effects (standing SBP) in normotensive men on stable dose terazosin (5 or 10 mg) following simultaneous administration of vardenafil 5 mg or placebo, or following administration of vardenafil 5 mg or placebo separated by 6 hours, are shown in Figure 4.
Study 2: This study was designed to evaluate the effect of 10 mg vardenafil (stage 1) and 20 mg vardenafil (stage 2) compared to placebo, when administered to a single cohort of BPH patients (n=23) on stable therapy with tamsulosin 0.4 mg or 0.8 mg daily for at least four weeks. The design was a randomized, double blind, two-period cross-over study. Vardenafil or placebo was given simultaneously with tamsulosin. Blood pressure and pulse were evaluated over the 6-hour interval after vardenafil dosing. For BP results see . One patient experienced a decrease from baseline in standing SBP of >30 mmHg following vardenafil 10 mg. There were no other instances of outlier blood pressure values (standing SBP <85 mmHg or decrease from baseline in standing SBP of >30 mmHg). Three patients reported dizziness following vardenafil 20 mg. There were no cases of syncope.
Blood pressure effects (standing SBP) in normotensive men on stable dose tamsulosin 0.4 mg following simultaneous administration of vardenafil 20 mg or placebo, or following administration of vardenafil 20 mg or placebo separated by 6 hours are shown in Figure 5.
Concomitant treatment with vardenafil and alpha-blockers should be initiated only if the patient is stable on his alpha-blocker therapy. In those patients who are stable on alpha-blocker therapy, LEVITRA should be initiated at the lowest recommended starting dose (see ).
Blood pressure effects in normotensive men after forced titration with alpha-blockers:
Two randomized, double blind, placebo-controlled clinical pharmacology studies with healthy normotensive volunteers (age range, 45-74 years) were performed after forced titration of the alpha-blocker terazosin to 10 mg daily over 14 days (n=29), and after initiation of tamsulosin 0.4 mg daily for five days (n=24). There were no severe adverse events related to hypotension in either study. Symptoms of hypotension were a cause for withdrawal in 2 subjects receiving terazosin and in 4 subjects receiving tamsulosin. Instances of outlier blood pressure values (defined as standing SBP <85 mmHg and/or a decrease from baseline of standing SBP >30 mmHg) were observed in 9/24 subjects receiving tamsulosin and 19/29 receiving terazosin. The incidence of subjects with standing SBP <85 mmHg given vardenafil and terazosin to achieve simultaneous T led to early termination of that arm of the study. In most (7/8) of these subjects, instances of standing SBP <85 mmHg were not associated with symptoms. Among subjects treated with terazosin, outlier values were observed more frequently when vardenafil and terazosin were given to achieve simultaneous T than when dosing was administered to separate T by 6 hours. There were 3 cases of dizziness observed with concomitant administration of terazosin and vardenafil. Seven subjects experienced dizziness mainly occurring with simultaneous T administration of tamsulosin. There were no cases of syncope.
Ritonavir and indinavir: Upon concomitant administration of 5 mg of LEVITRA with 600 mg BID ritonavir, the C and AUC of ritonavir were reduced by approximately 20%. Upon administration of 10 mg of LEVITRA with 800 mg TID indinavir, the C and AUC of indinavir were reduced by 40% and 30%, respectively.
Alcohol: Alcohol (0.5 g/kg body weight: approximately 40 mL of absolute alcohol in a 70 kg person) and vardenafil plasma levels were not altered when dosed simultaneously. LEVITRA (20 mg) did not potentiate the hypotensive effects of alcohol during the 4-hour observation period in healthy volunteers when administered with alcohol (0.5 g/kg body weight).
Aspirin: LEVITRA (10 mg and 20 mg) did not potentiate the increase in bleeding time caused by aspirin (two 81 mg tablets).
Other interactions: LEVITRA had no effect on the pharmacodynamics of glyburide (glucose and insulin concentrations) and warfarin (prothrombin time or other pharmacodynamic parameters).
Prescribing Erythromycin Base Filmtab tablets in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.
Since erythromycin is principally excreted by the liver, caution should be exercised when erythromycin is administered to patients with impaired hepatic function. (See and .)
There have been reports that erythromycin may aggravate the weakness of patients with myasthenia gravis.
There have been reports of infantile hypertrophic pyloric stenosis (IHPS) occurring in infants following erythromycin therapy. In one cohort of 157 newborns who were given erythromycin for pertussis prophylaxis, seven neonates (5%) developed symptoms of non-bilious vomiting or irritability with feeding and were subsequently diagnosed as having IHPS requiring surgical pyloromyotomy. A possible dose-response effect was described with an absolute risk of IHPS of 5.1% for infants who took erythromycin for 8-14 days and 10% for infants who took erythromycin for 15-21 days. Since erythromycin may be used in the treatment of conditions in infants which are associated with significant mortality or morbidity (such as pertussis or neonatal infections), the benefit of erythromycin therapy needs to be weighed against the potential risk of developing IHPS. Parents should be informed to contact their physician if vomiting or irritability with feeding occurs.
Prolonged or repeated use of erythromycin may result in an overgrowth of nonsusceptible bacteria or fungi. If superinfection occurs, erythromycin should be discontinued and appropriate therapy instituted.
When indicated, incision and drainage or other surgical procedures should be performed in conjunction with antibiotic therapy.
Patients should be counseled that antibacterial drugs including Erythromycin Base Filmtab tablets should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When Erythromycin Base Filmtab tablets is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by Erythromycin Base Filmtab tablets or other antibacterial drugs in the future.
Erythromycin use in patients who are receiving high doses of theophylline may be associated with an increase in serum theophylline levels and potential theophylline toxicity. In case of theophylline toxicity and/or elevated serum theophylline levels, the dose of theophylline should be reduced while the patient is receiving concomitant erythromycin therapy.
Concomitant administration of erythromycin and digoxin has been reported to result in elevated digoxin serum levels.
There have been reports of increased anticoagulant effects when erythromycin and oral anticoagulants were used concomitantly. Increased anticoagulation effects due to interactions of erythromycin with oral anticoagulants may be more pronounced in the elderly.
Erythromycin is a substrate and inhibitor of the 3A isoform subfamily of the cytochrome p450 enzyme system (CYP3A). Coadministration of erythromycin and a drug primarily metabolized by CYP3A may be associated with elevations in drug concentrations that could increase or prolong both the therapeutic and adverse effects of the concomitant drug. Dosage adjustments may be considered, and when possible, serum concentrations of drugs primarily metabolized by CYP3A should be monitored closely in patients concurrently receiving erythromycin.
The following are examples of some clinically significant CYP3A based drug interactions. Interactions with other drugs metabolized by the CYP3A isoform are also possible. The following CYP3A based drug interactions have been observed with erythromycin products in post-marketing experience:
Concurrent use of erythromycin and ergotamine or dihydroergotamine has been associated in some patients with acute ergot toxicity characterized by severe peripheral vasospasm and dysesthesia.
Erythromycin has been reported to decrease the clearance of triazolam and midazolam, and thus, may increase the pharmacologic effect of these benzodiazepines.
Erythromycin has been reported to increase concentrations of HMG-CoA reductase inhibitors (e.g., lovastatin and simvastatin). Rare reports of rhabdomyolysis have been reported in patients taking these drugs concomitantly.
Erythromycin has been reported to increase the systemic exposure (AUC) of sildenafil. Reduction of sildenafil dosage should be considered. (See Viagra package insert.)
There have been spontaneous or published reports of CYP3A based interactions of erythromycin with cyclosporine, carbamazepine, tacrolimus, alfentanil, disopyramide, rifabutin, quinidine, methylprednisolone, cilostazol, vinblastine, and bromocriptine.
Concomitant administration of erythromycin with cisapride, pimozide, astemizole, or terfenadine is contraindicated. (See .)
In addition, there have been reports of interactions of erythromycin with drugs not thought to be metabolized by CYP3A, including hexobarbital, phenytoin, and valproate.
Erythromycin has been reported to significantly alter the metabolism of the nonsedating antihistamines terfenadine and astemizole when taken concomitantly. Rare cases of serious cardiovascular adverse events, including electrocardiographic QT/QT interval prolongation, cardiac arrest, torsades de pointes, and other ventricular arrhythmias, have been observed. (See .) In addition, deaths have been reported rarely with concomitant administration of terfenadine and erythromycin.
There have been post-marketing reports of drug interactions when erythromycin was co-administered with cisapride, resulting in QT prolongation, cardiac arrhythmias, ventricular tachycardia, ventricular fibrillation, and torsades de pointes, most likely due to the inhibition of hepatic metabolism of cisapride by erythromycin. Fatalities have been reported. (See ).
Erythromycin interferes with the fluorometric determination of urinary catecholamines.
Long-term (2-year) oral studies conducted in rats with erythromycin base did not provide evidence of tumorigenicity. Mutagenicity studies have not been conducted. There was no apparent effect on male or female fertility in rats fed erythromycin (base) at levels up to 0.25 percent of diet.
There is no evidence of teratogenicity or any other adverse effect on reproduction in female rats fed erythromycin base (up to 0.25 percent of diet) prior to and during mating, during gestation, and through weaning of two successive litters. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.
The effect of erythromycin on labor and delivery is unknown.
Erythromycin is excreted in human milk. Caution should be exercised when erythromycin is administered to a nursing woman.
See and .
The most frequent side effects of oral erythromycin preparations are gastrointestinal and are dose-related. They include nausea, vomiting, abdominal pain, diarrhea and anorexia. Symptoms of hepatitis, hepatic dysfunction and/or abnormal liver function test results may occur. (See .)
Onset of pseudomembranous colitis symptoms may occur during or after antibacterial treatment. (See .)
Erythromycin has been associated with QT prolongation and ventricular arrhythmias, including ventricular tachycardia and torsades de pointes.
Allergic reactions ranging from urticaria to anaphylaxis have occurred. Skin reactions ranging from mild eruptions to erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis have been reported rarely.
There have been rare reports of pancreatitis and convulsions.
There have been isolated reports of reversible hearing loss occurring chiefly in patients with renal insufficiency and in patients receiving high doses of erythromycin.
Reference
This information is obtained from the National Institute of Health's Standard Packaging Label drug database.
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Clonazepam Description Each single-scored tablet, for oral administration, contains 0.5 mg, 1 mg, or 2 mg Clonazepam, USP, a benzodiazepine. Each tablet also contains corn starch, lactose monohydrate, magnesium stearate, microcrystalline cellulose, and povidone. Clonazepam tablets USP 0.5 mg contain Yellow D&C No. 10 Aluminum Lake. Clonazepam tablets USP 1 mg contain Yellow D&C No. 10 Aluminum Lake, as well as FD&C Blue No. 1 Aluminum Lake. Chemically, Clonazepam, USP is 5-(o-chlorophenyl)-1,3-dihydro-7-nitro-2H-1,4-benzodiazepin-2-one. It is a light yellow crystalline powder. It has the following structural formula: C15H10ClN3O3 M.W. 315.72Tips
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